SN65HVD230 two-node CAN physical-state experiment

Target: original Raspberry Pi Pico with MicroPython v1.29.0.
Copy can_states.py to the device. In its REPL:
    from can_states import run
    run("r")
    run("a")
    run("b")
    run("x")
Arm the scope before each dominant command. Unplug USB before rewiring.

Host: with Python 3, from the extracted archive:
    PYTHONDONTWRITEBYTECODE=1 python3 test_actual_program.py -v
The host suite runs can_states.py against fake Pin and sleep_us functions.
No Pico, test instrument, CAN controller or third-party Python package is needed.

Read the full article for setup and grounding. Keep both scope references at
common 0 V, use one 120 ohm resistor at each end, and verify unpowered first.
The figures and state table are predictions. No physical capture or target run
is supplied. Record your own data in observations-blank.csv.
